They'd never clash. Progenitus having protection from everything means that it would stroll straight past Emmy and Emrakul would survive the 10 damage if it swung at the opposing player. I suppose Progenitus since it would murder your opponent in 2 turns, but that presupposes that it swings first.
In larger answers, there are way too many variables and the capabilities of each are basically unknown. It's not something that can really be debated with any meaningful data because of the vast swathes of missing information.
Kind of impossible to tell. There's limited scale offered in both Emrakul and Progenitus's art. All we get is that two pieces show atmospheric distortion, which means they're both... reaaaally big.
This is storyline speculation. Cards stats shouldn't be used. Otherwise Gerrard Capashen would have lost against Tsabo Tavoc.
Let me put it like this, there is NO answer to this and by sticking to the cards I can actually provide an answer that's not just "This is not a viable question."
Because it isn't.
I suppose that's fair. Unless the Eldrazi somehow found their way to Alara, I guess we'll never know. (This is not speculating that they will. I've seen too many Eldrazi speculations turn to "This will absolutely not happen" to speculate what they will do next.)
This kind of threads make me wonder if some nerds ever watch sports. Asking "how would win in a fight between such and such" is as ridiculous as asking "who would win in a match between this team and this other team?". The answer is always "who knows, too many variables to consider."
In larger answers, there are way too many variables and the capabilities of each are basically unknown. It's not something that can really be debated with any meaningful data because of the vast swathes of missing information.
Let me put it like this, there is NO answer to this and by sticking to the cards I can actually provide an answer that's not just "This is not a viable question."
Because it isn't.
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Special thanks to Serrot_29 for Catbug'mrakul!